DESCRIPTION The goals of the parent project are to study the physiological significance, regulation, and structure of monoacylglycerol acyltransferase, a tissue specific microsomal enzyme expressed at high levels in neonates, in hibernating animals, and in migrating birds. During the course of their studies, the applicants obtained results that suggested that cells contain at least two separate pools of diacylglycerol that are not equally available for triacylglycerol and phospholipid synthesis. The goal of this proposal is to elucidate the pathways by which potentially different diacylglycerol pools contribute to the interconversion of cellular glycerolipids. Specifically, experiments are proposed to determine if diacylglycerol is used for triacylglycerol or phospholipid depending upon whether it originates from de novo synthesis, from hydrolyzed triacylglycerol, or from the action of phospholipase C. In addition, experiments are proposed to investigate the fate of diacylglycerol in CHO cells deficient in CTP:phosphocholine cytidylyltransferase and CTP:phosphoethanolamine cytidylyltransferase. Lastly, the applicants will investigate lipid recycling during the cell cycle.